Web guide control, web processing apparatus and method for operating the same

ABSTRACT

A web guide control for guiding a web, the web guide control having a first guide roller ( 201 ) and a second guide roller wherein the first guide roller ( 201 ) comprises an adjustment unit ( 310 ), the second guide roller comprises a tension measurement unit ( 300 ), and the web guide control comprises a data connection for supporting the adjustment unit with tension data from the tension measurement unit.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a web guide control and a webprocessing apparatus. The present invention relates particularly to aweb guide control for compensating failures in the raw material and/orthe coiling installation and to a web processing apparatus for coatingweb in vacuum installations. The present invention also relates to amethod for guiding a web and particularly to a method for compensatingfailures in a web during web guiding.

BACKGROUND OF THE INVENTION

Web handling is an important issue in installations for processingcontinuous web. Therein, many coils handling hundreds of metres or evenkilometres of web have to be arranged and operated in such a way that nodamage such as crinkles, trumlines, tear-offs, or the like occur in theweb.

It is of course undesirable that failures occur during the webprocessing such as the web coating. These failures may lead to the totalstop of production and/or to the rejection of parts or the entire webtreated. In other words, a web guiding malfunction can be very expensiveand time consuming.

In order to avoid malfunctions of a web processing apparatus it is knownin the art to provide each guide roll of the web guiding apparatus witha specific tolerance. This way a difference up to e.g. 0.02 mm in theweb's thickness along the width of the web can be handled. However, ininstallations with long coiling length the addition of the guide rollerbearing tolerances can cause a tilted feeding in the installation.Further, in vacuum applications very small deviations in thickness cancause complications or failure which would not occur at ambientpressure.

SUMMARY OF THE INVENTION

The problems in the state of the art are at least partly overcome by theweb guide control according to claim 1, the web processing apparatusaccording to claim 10 and the method for guiding a web according toclaim 12. Further aspects, details and advantages are apparent by thedependent claims, the description and the accompanying drawings.

In view of the above, a web guide control for guiding a web is provided.The web guide control includes two guide rollers, an adjustment unit atthe first guide roller, a tension measurement unit at the second guideroller, and a data connection for supporting the adjustment unit withtension data from the tension measurement unit.

According to another aspect of the present invention a web processingapparatus with at least one guide control as described herein isprovided.

According to another aspect of the present invention, a method forguiding a web is provided. The method includes the steps of adjustingthe position of a first guide roller by moving one side of the firstguide roller and measuring the tension of the web acting on a secondguide roller, thereby receiving measurement results, wherein adjustingis based on the measurement results.

A typical application of web processing apparatuses is the high vacuumweb film deposition. For instance, in these applications a protectivelayer is deposited on a packaging substrate like thin plastic, paper, ormetal foil. Thin metal or oxide films may be deposited on the packagingsubstrate for creating a moisture or oxygen barrier promoting freshnessand extending the shelf life of the consumer products which use thesefilms.

A further application of a web processing apparatus is the field ofmanufacturing electronic products. A conductive layer may be depositedon the web serving as conductive coating in applications such ascapacitor and touch panels.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will becomemore apparent from the following detailed description of preferredembodiments thereof with reference to the attached drawings in which:

FIG. 1 shows a schematic diagram of an embodiment of a web processingapparatus according to the present invention.

FIG. 2 shows a schematic diagram in a cross-sectional view of the webguide control system according to an embodiment of the presentinvention.

FIG. 3 shows a schematic diagram in a plain section view of the webguide control system according to another embodiment of the presentinvention.

FIG. 4 shows a schematic diagram in a plain section view of the webguide control system according to another embodiment of the presentinvention.

FIG. 5 shows a flow chart of the method for guiding a web according toan embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the various embodiments of theinvention, one or more examples of which are illustrated in the figures.Each example is provided by way of explanation of the invention, and isnot meant as a limitation of the invention. For example, featuresillustrated or described as part of one embodiment can be used on or inconjunction with other embodiments to yield yet a further embodiment. Itis intended that the present invention includes such modifications andvariations.

FIG. 1 shows an embodiment of a web processing apparatus where web guidecontrol 10 according to the present invention is implemented. The webprocessing apparatus comprises a web processing unit 100 where a web 140is fed to. Further, a web storage unit 110 is shown where the web 140 iscoiled. The web 140 enters the web processing unit 100 via the inletport 120. The processed web 150 is guided out of the web processing unit100 through the outlet port 130. Some installations, in particular atambient pressure, do not use inlet or outlet port or other units whichwould be denoted as such. Typically, the web processing unit 100comprises one, two, three, or more web guide controls according to thepresent invention for serial web processing. Synonyms to the term “web”as used within the present application are strip, flexible substrate orthe like.

Typically, a web is a three dimensional solid body the thickness ofwhich is in the range up to 1 mm, more typically between 1 μm and 500μm, and the width of which is between 10 cm and 4.5 m, more typicallybetween 30 cm and 3 m. In typical embodiments, the length of a web islarger than 10 m. Typically, a web consists of a continuous sheet ofthin and flexible material. Typical web materials are metals, plastics,paper, or the like.

According to an embodiment of the present invention, the web 140 is fedto the web processing unit 100 from a web supply. Typically, the websupply is a web storage unit 110 where the web is coiled. Typicallengths of the web on the coil are in the range between 500 m and 50 km.In other embodiments, the web supply is continuous e.g. from a sectionwith or without an outlet port where the web exits the section for beingfed to the web processing unit 100 (not shown). Typical guidingvelocities are in the range of between 0.1 and 20 metre per second.Typically, different processing steps are performed in the webprocessing unit 100 such as cleaning, coating, cooling, heating, orstructuring the web.

After the web has been processed in the web processing unit 100, theprocessed web 150 exits the web processing unit 100 at the outlet port130. Typically, the processed web 150 is fed to a second processing unitor guided out for storage.

Typically, a web processing apparatus comprising one or more web guidecontrols according to the present invention may be used for guiding aweb in various applications. This web processing apparatus isparticularly suitable for challenging webs such as a metal web, inparticular aluminium web, and thin plastic web. Thin web in this contextis meant to be understood as having a thickness of between 1 μm and 200μm, in particular between 30 μm and 140 μm.

FIG. 2 shows a cross-sectional view of an embodiment of the web guidecontrol 10 of the present invention. The web guide control 10 comprisesa first guide roller 201 with its corresponding shaft axis 205 and asecond guide roller 202 with its corresponding shaft axis 215. The web140 is guided through the first guide roller 201 and the second guideroller 202. The web 140 may be unprocessed or have already undergone oneor more processing steps. Typically the first guide roller 201 ispositioned upstream of the second guide roller 202. The terms“downstream” and “upstream” within the present application are to beunderstood with respect to the travelling direction of the web. The webguide control 10 of the present invention is not exclusively limited tothe implementation in web processing apparatus. For example, the webguide control can also be implemented in manufacturing plants where webtransport is required. In principal, it is also possible to position thefirst guide roller 201 downstream of the second guide roller 202.

According to the present invention the distance between both shaft axes205 and 215 can be adjusted to compensate for transversal tension actingon the web travelling between both guide rollers 201 and 202. To allowfor compensation, the second guide roller is equipped with a web tensionmeasurement unit such as a tension sensor. A tension sensor may be apiezoresistive or piezoelectric tension sensor. Alternatively, thesensor may be equipped with a hall element or a capacitor in order todetermine the tension. In other embodiments, both the first guide rollerand the second guide roller are equipped with tension measurement units.According to an embodiment of the present invention which is shown inthe drawings, the web tension measurement unit is enclosed in the secondguide roller 202. Typically, the measurement sensor is adapted formeasuring tensions of between 0 and 400 N/m. Typically this distance isadjusted using an adjustment unit placed at one side of the first guideroller 201. The “side” of the roller is to be understood as the positionat or close to the end of the roller or its axis. Typical diameters ofguide rollers used in the present invention are between 65 mm and 300mm.

The advantage of using a two roller system for measurement andadjustment instead of a single roller system is, for example, a betterhandling of vibrations caused by the control loop.

In principle the adjustment unit may be applied for alignment of theguide rollers required to avoid transversal tension acting on the web.Typically the web guide control 10 of the present invention isparticularly useful for compensating different coiling strengths at theguide rollers 201 and 202. Different coiling strength is most typicallya result of different thickness of the web along its width. This couldresult in tilted feeding and, subsequently, varying contact betweenguiding rollers and web which can go along with thermal complications.Typically shorter distances of less than 1 m between the axis ofadjacent guide rollers are more critical to the proper handling of theweb.

In some embodiments of the present invention, the first guide roller 201and/or the second guide roller 202 are cooling or heater rollers.Alternatively, or in addition, there might be positioned a furthercooling or heater guide roller in between the first guide roller 201 andthe second guide roller 202, upstream of the first and second guideroller 201 and 202, or downstream of the first and second guide roller.Other processing steps such as cleaning or coating may be undertakenbefore, the first guide roller, between the first guide roller and thesecond guide roller, or after the second guide roller.

FIG. 3 shows a plain view of a typical embodiment of the presentinvention. The different elements of this embodiment forming part of thetransversal web tension adjustment are shown in the figure: anadjustment unit 310 at the first guide roller 201, a web tensionmeasurement unit 300 at the second guide roller 202, and a dataconnection 330 between both guide rollers 201 and 202 to supply tensiondata to the adjustment unit 310. Typically, the first guide roller 201is positioned upstream of the second guide roller 202.

The data connection 330 is used to transmit information from themeasurement unit to the adjustment unit 310. The data connection 330 canalso be used to transmit information from the adjustment unit 310 to anexternal interface. Typically this interface consists of a personalcomputer which processes the data from the adjustment unit 310. Also theinterface can consist of an analogue front panel comprising differentelement to tune the adjustment unit 310, i.e. using differentpotentiometers, dials, switches, and displays. Further, the interfacecan also consist of a digital device including numeric pads, graphicaldisplay, text commands, or a graphical user interface. Typically, allthese interfaces include different features such as controller function,calibration of the system, compensation of ambient conditions, oracquisition and recording of waveforms from the tension unit 300 or theadjustment unit 310.

For connecting the data connection 330 to the different devices,different port types are used. Typically, when serial communication isused, the ports are RS232, RS422, RS485, or universal serial bus (USB)ports. Typically, parallel communication devices are used whencommunication between the data connection 330 and a computer isrequired. Most often used parallel communication devices are DB-25,Centronics 36, SPP, EPP or ECP parallel ports. The data connection 330can be used to make the adjustment unit 310 compatible withtransistor-transistor logic (TTL) or with programmable logic controllers(PLC). Additionally the data connection 330 can be used to connect theadjustment unit 310 with a network.

According to an embodiment of the present invention the tension actingon both shaft axes 215 and 216 of the second guide roller 202 will beacquired separately. The acquired data will be processed and sent to theadjustment unit 310 in the first guide roller 201. The adjustment unit310 adjusts the position of the shaft axis at one side of the firstguide roller 201. Thereby, the distance between the shaft axes of thefirst guide roller and the shaft axes of the second guide roller isadjusted. The adjustment unit 300 is operated in order to equalize thetension measured between the shaft axes at both sides of the secondguide roller 202. It is, however, also possible to adjust the positionof the shaft axis on both sides of the first guide roller 201 (not shownin drawings).

FIG. 4 shows a plain view of another embodiment of the web guide control10 of the present invention where the adjustment unit consists of arotating shaft axis 420 and a translation element 411. The web tensionmeasurement units 300 are placed at the bearings 431 and 432 of thesecond guide roller 202. Typically the translation element 411 enclosesa drive 410, such as a motor, and a moving bearing 415 which can bedisplaced along the machine frame 452. The shaft axis 206 is attached tothe moving bearing 415 enclosing the drive 410. The rotating shaft axis420 encloses the shaft axis 205 which is attached with rotationalfreedom to the machine frame 451.

Different kind of motors can be used in the adjustment unit of thepresent invention. At the first guide roller 201 the distance betweenthe bearings of the two guide rollers 201 and 202 can be adjusted on oneside. In order to do so, a powered engine is typically used. Typically,the drive for adjustment is either an electrical or hydraulic motoraccording to the present invention. The position of the moving bearing415 of the first guide roller 201 is adjusted in such a way that bothtension measurement sensors in the second guide 202 roller face the sameloading.

In typical embodiments of the present invention the web tensionmeasurement units consists of a transducer and a strain gauge. Typicallythe transducer consists of a beam which stretches or compresses inresponse to varying tensions. The strain gauge measures thecorresponding change in electrical resistance. Typically, themeasurement performed by the strain gauge is amplified and converted toa voltage or current for further processing. In general, the web tensionmeasurement units enclose an analogue or digital front end, for furtherprocessing of the tension measurement. Typically, the web tensionmeasurement units are aligned in order to maximize the measurement ofthe tension in the travelling direction of the web between the first andthe second guide rollers. Typically, the web tension measurement unitsare mounted in the guide rollers using different options, i.e., betweenpillow blocks, using cantilevered brackets, using securing via a flangeor clamp, using studs, or threaded into through-holes.

FIG. 5 shows a signal flow chart for the web guide control systemaccording to an embodiment of the present invention, which includes aclosed-loop controller based on a negative feedback 500 of thetransversal tension measurement. The closed-loop system maintains anoutput of the controlled system, e.g. the feedback signal 533, equal toa setpoint 534 value by using previous values of the feedback signal 533and a control signal 532 fed to the controlled system which is an outputof the controller itself. The main elements of the flow chart are acontroller 501 and a web guide system 502 constituting the web guidecontrol 10 according to the present invention. The tension differencebetween both sides of the second guide roller 202 is the feedback signal533. Typically, the setpoint 534 at the controller of the presentinvention has a null value in order to compensate for tensiondifferences which correspond to transversal tensions acting on the web.Therefore, in typical embodiments of the present invention, the error531 of the controller exactly corresponds to the tension differencemeasurement, i.e. the feedback signal 533. In typical embodiments of thepresent invention the controller compensates deviations from zero of theerror 531 using the adjustment unit 310. Typically, this error 531compensation translates to a distance adjustment of the shaft axes 205and 215 at one side of both guide rollers 201 and 202. Therefore, thecontrol signal 532, e.g. the controller output, typically corresponds tothe distance between the shaft axes at one side of both guide rollers201 and 202.

In principle, different control approaches can be implemented in thecontroller 501. Typically, a linear control approach is implemented inthe controller 501 choosing from: proportional, integral and derivative(PID) control; proportional and integral (PI) control; proportional andderivative (PD) control; and proportional (P) control. However, alsoother advanced controls using non-linear control approaches may beimplemented in embodiments of the present invention, e.g. adaptive gain,dead-time compensation, fuzzy logic, neural networks, or feed-forwardcontrol. Controllers implemented in the present application can beanalogue or digital interfaces including compatibility withtransistor-transistor logic (TTL). Typically, digital interfaces worksin a discrete manner where the values for the adjustment unit arerefreshed after a certain and fixed time period Δt. Other specialfeatures can be present in controllers of the present invention such asself-tuning, signal computation or filtering, or built-in indicators.

As illustration of the functioning of a controller according to anembodiment of the present invention, in the following the implementationof a discrete PID controller is described. The feedback signal at agiven control step i corresponds to the difference between both tensionmeasurements T_(i) ²¹⁵ and T_(i) ²¹⁶. Typically, for embodimentscorresponding to the present invention, the setpoint is kept at zerosince the controller has to compensate for transversal forces acting onthe web, i.e. the tension at both sides of the second guide roller 202should be equal. Therefore, the error signal at a given processing stepi corresponds to

E _(i) =T _(i) ²¹⁵ −T _(i) ²¹⁶.

The PID controller calculates the output value D_(i+1) by using:

D _(i+1) =D _(i) +K _(p) E _(i) +K _(d)(E _(i) −E _(i−1)),

where the first term corresponds to the integral part of the controller,the second to the proportional, and the third to the derivative. K_(p)is the proportional band and K_(d) is the derivative gain. Typically,values of D_(i+1)-D_(i) other than zero correspond to a variation in theposition at one side of the first guide roller 201. In other embodimentsof the present invention, this corresponds to the signal for operationof the drive 410 at the adjustment unit in the first guide roller 201.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. While the invention has beendescribed in terms of various specific embodiments, those skilled in theart will recognize that the invention can be practiced with modificationwithin the spirit and scope of the claims. Especially, mutuallynon-exclusive features of the embodiments described above may becombined with each other. The patentable scope of the invention isdefined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims of they have structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

1. A web guide control for guiding a web, the web guide control having afirst guide roller, and a second guide roller wherein the first guideroller comprises an adjustment unit; the second guide roller comprises atension measurement unit wherein the first guide roller is positioneddownstream of the second guide roller with respect to the web guidingdirection; and the web guide control comprises a data connection forsupporting the adjustment unit with tension data from the tensionmeasurement unit.
 2. The web guide control according to claim 1 whereinthe tension measurement unit comprises a first tension sensor positionedat a first side of the second guide roller.
 3. The web guide controlaccording to claim 1 wherein the tension measurement unit comprises asecond tension sensor positioned at a second side of the second guideroller.
 4. The web guide control according to claim 1 wherein theadjustment unit comprises a motor for moving the first guide rollerpositioned at one side of the first guide roller.
 5. The web guidecontrol according to claim 1 wherein the adjustment unit is controlledusing a closed-loop controller and the tension data is used as variablefeedback signal.
 6. The web guide control according to claim 5 whereinthe closed-loop comprises analogue electronics.
 7. The web guide controlaccording to claim 5 wherein the closed-loop comprises digitalelectronics.
 8. A web processing apparatus having at least one web guidecontrol for guiding a web, the web guide control having a first guideroller, and a second guide roller wherein the first guide rollercomprises an adjustment unit; the second guide roller comprises atension measurement unit wherein the first guide roller is positioneddownstream of the second guide roller with respect to the web guidingdirection; and the web guide control comprises a data connection forsupporting the adjustment unit with tension data from the tensionmeasurement unit.
 9. The web processing apparatus according to claim 8wherein the tension measurement unit comprises a first tension sensorpositioned at a first side of the second guide roller.
 10. The webprocessing apparatus according to claim 8 wherein the tensionmeasurement unit comprises a second tension sensor positioned at asecond side of the second guide roller (202).
 11. The web processingapparatus according to claim 8 wherein the adjustment unit comprises amotor for moving the first guide roller positioned at one side of thefirst guide roller.
 12. The web processing apparatus according to claim8 wherein the adjustment unit is controlled using a closed-loopcontroller and the tension data is used as variable feedback signal. 13.The web processing apparatus according to claim 12 wherein theclosed-loop comprises analogue electronics.
 14. The web processingapparatus according to claim 12 wherein the closed-loop comprisesdigital electronics.
 15. The web processing apparatus according to claim8, further comprising a coating unit for coating the web.
 16. A methodfor guiding a web comprising the steps of: adjusting the position of afirst guide roller by moving one side of the first guide roller;measuring the tension of the web acting on a second guide roller,thereby receiving measurement results, wherein the measuring isundertaken upstream of the adjusting with respect to the web guidingdirection; and wherein adjusting is based on the measurement results.17. The method according to claim 16 wherein the measuring is undertakenat a first side of a second guide roller and at a second side of thesecond guide roller.
 18. The method according to claim 16 wherein theadjusting is undertaken at one side of the first guide roller.